The long-term objectives of this proposal are to provide answers to three fundamental questions concerning translational regulation of adenovirus gene expression of infected cells. (1) How do adenoviruses overcome the interferon induced antiviral responses? (2) How do adenoviruses control the host cell translation machinery for the preferential translation of viral mRNAs at late times after infection? (3) What is the mechanism and function of the late viral 5' noncoding region (tripartite leader) in translation regulation? This proposal is designed to integrate two complementing areas of translation research; the enzymology of the interferon induced antiviral state, and the ability of adenovirus to take-over the host cell translation machinery. First, recombinant interferons will be used to elucidate the molecular mechanism by which adenovirus VA1 RNA inhibits activation of the interferon induced, P1/eIF2 alpha kinase. Adenoviruses are generally insensitive to the effects of interferon, and the anti-kinase activity associated with VA1 RNA is very likely responsible. Second, the role of the tripartite leader, and its possible interaction with VA1 RNA and the 18S ribosomal RNA, will be investigated to determine the mechanism for preferential translation of adenovirus MRNAs at late times after infection. A thorough genetic and biochemical analysis will be undertaken to determine the sequence requirements for tripartite leader function. Analysis of cells infected with adenoviruses in a VA1 + and - genetic background represents a unique and favorable system for investigation of translation regulateion. It is one of very few systems in which a mutational and biochemical analysis is possible for translation regulation by 5' noncoding regions, interferon induced antiviral activities, and viral responses to these cellular mechanisms. The specific aims of this proposal are: (1) To investigate the mechanism by which Ad VA1 RNA antagonizes the activation of the interferon induced, P1/eIF2 alpha kinase. (2) To investigate the mechanism by which the Ad tripartite leader enhances translation. (3) To investigate the preferential translation of tripartite leader containing mRNAs at late times after infection.